A stool analysis is a series of tests done on a stool (feces) sample to help diagnose certain conditions affecting the digestive tract. These conditions can include infection (such as from parasites, viruses, or bacteria), poor nutrient absorption, or cancer.
For a stool analysis, a stool sample is collected in a clean container and then sent to the laboratory. Laboratory analysis includes microscopic examination, chemical tests, and microbiologic tests. The stool will be checked for color, consistency, amount, shape, odor, and the presence of mucus. The stool may be examined for hidden (occult) blood, fat, meat fibers, bile, white blood cells , and sugars called reducing substances. The pH of the stool also may be measured. A stool culture is done to find out if bacteria may be causing an infection.
WHY IT IS DONE
Stool analysis is done to:
- Help identify diseases of the digestive tract, liver, and pancreas . Certain enzymes (such as trypsin or elastase) may be evaluated in the stool to help determine how well the pancreas is functioning.
- Help find the cause of symptoms affecting the digestive tract, including prolonged diarrhea, bloody diarrhea, an increased amount of gas, nausea, vomiting, loss of appetite, bloating, abdominal pain and cramping, and fever.
- Screen for colon cancer by checking for hidden (occult) blood.
- Look for parasites, such as pinworms or GiardiaGiardia.
- Look for the cause of an infection, such as bacteria, a fungus, or a virus.
- Check for poor absorption of nutrients by the digestive tract (malabsorption syndrome). For this test, all stool is collected over a 72-hour period and then checked for fat (and sometimes for meat fibers). This test is called a 72-hour stool collection or quantitative fecal fat test.
Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form.
HOW TO PREPARE
Many medicines can change the results of this test. You will need to avoid certain medicines depending on which kind of stool analysis you have. You may need to stop taking medicines such as antacids, antidiarrheal medicines, antiparasite medicines, antibiotics, laxatives, or nonsteroidal anti-inflammatory drugs (NSAIDs) for 1 to 2 weeks before you have the test. Be sure to tell your doctor about all the nonprescription and prescription medicines you take.
ABOUT STOOL TESTS
Stool (or feces) is usually thought of as nothing but waste — something to quickly flush away. But bowel movements can provide doctors with valuable information as to what’s wrong when a child has a problem in the stomach, intestines, or another part of the gastrointestinal system.
- A doctor may order a stool collection to test for a variety of possible conditions, including:
- allergy or inflammation in the body, such as part of the evaluation of milk protein allergy in infants
- infection, as caused by some types of bacteria, viruses, or parasites that invade the gastrointestinal system
- digestive problems, such as the malabsorption of certain sugars, fats, or nutrients
- bleeding inside of the gastrointestinal tract
The most common reason to test stool is to determine whether a type of bacteria or parasite may be infecting the intestines. Many microscopic organisms living in the intestines are necessary for normal digestion. If the intestines become infected with harmful bacteria or parasites, though, it can cause problems like certain types of bloody diarrhea, and testing stool can help find the cause.
Stool samples are also sometimes analyzed for what they contain; for instance, examining the fat content. Normally, fat is completely absorbed from the intestine, and the stool contains virtually no fat. In certain types of digestive disorders, however, fat is incompletely absorbed and remains in the stool.
COLLECTING A STOOL SPECIMEN
Unlike most other lab tests, stool is sometimes collected by the child’s family at home, not by a health care professional. Here are some tips for collecting a stool specimen:
- Collecting stool can be messy, so be sure to wear latex gloves and wash your hands and your child’s hands well afterward.
- Many kids with diarrhea, especially young children, can’t always let a parent know in advance when a bowel movement is coming. Sometimes a hat-shaped plastic lid is used to collect the stool specimen. This catching device can be quickly placed over the toilet bowl or your child’s rear end to collect the specimen. Using a catching device can prevent contamination of the stool by water and dirt. If urine contaminates the stool sample, it will be necessary to take another sample. Also, if you’re unable to catch the stool sample before it touches the inside of the toilet, the sample will need to be repeated. Fishing a bowel movement out of the toilet does not provide a clean specimen for the laboratory to analyze.
- Another way to collect a stool sample is to loosely place plastic wrap across the rim of the toilet, under the seat. Then place the stool sample in a clean, sealable container before taking to the laboratory. Plastic wrap can also be used to line the diaper of an infant or toddler who is not yet using the toilet.
The stool should be collected into clean, dry plastic jars with screw-cap lids. You can get these from your doctor or through hospital laboratories or pharmacies, although any clean, sealable container could do the job. For best results, the stool should then be brought to the laboratory immediately.
If the stool specimen is going to be examined for an infection, and it’s impossible to get the sample to the laboratory right away, the stool should be refrigerated, then taken to the laboratory to be cultured as soon as possible after collection. When the sample arrives at the lab, it is either examined and cultured immediately or placed in a special liquid medium that attempts to preserve potential bacteria or parasites.
The doctor or the hospital laboratory will usually provide written instructions on how to successfully collect a stool sample; if written instructions are not provided, take notes on how to collect the sample and what to do once you’ve collected it.
If you have any questions about how to collect the specimen, be sure to ask. The doctor or the lab will also let you know if a fresh stool sample is needed for a particular test, and if it will need to be brought to the laboratory right away.
Most of the time, disease-causing bacteria or parasites can be identified from a single stool specimen. Sometimes, however, up to three samples from different bowel movements must be taken. The doctor will let you know if this is the case.